The prior art filter apparatus having a bag with a resilient gasket is described in U.S. Pat. No. 4,460,468, issued Jul. 17, 1984. Related patents include U.S. Pat. Nos. 3,771,664, issued Nov. 13, 1973, 4,133,769, issued Jan. 9, 1979, 4,204,966, issued May 27, 1980, 4,259,188, issued Mar. 31, 1981, 4,285,814, issued Aug. 25, 1981, 4,419,240, issued Dec. 6, 1983, 4,460,468, issued Jul. 17, 1984, 4,490,253, issued Dec. 25, 1984, and 4,669,167, issued Jun. 2, 1987.
The prior art filter apparatus having a bag with a resilient gasket includes a housing, a cover plate, and a bag filter subassembly. The bag filter subassembly has a filter bag and a rubber seal member. The seal member has a web portion and a peripheral head portion for forming a seal between the housing and the cover plate, the rubber seal being attached to the bag filter at its open end by an adhesive or heat seal.
One problem with the prior art filter apparatus is that there is no way to tell if the seal member and the filter bag are in place, except by removing the cover plate.